Upload
rashad
View
30
Download
3
Tags:
Embed Size (px)
DESCRIPTION
Texture Synthesis on Surfaces. Paper by Greg Turk Presentation by Jon Super. Texture Synthesis on Surfaces. +. Goals of texture placement. Take a 2D texture and wrap it onto a surface Avoid noticeable seams between patches Minimize stretching and distortion - PowerPoint PPT Presentation
Citation preview
Texture Synthesis on Surfaces
Paper by Greg TurkPaper by Greg Turk
Presentation by Jon SuperPresentation by Jon Super
Texture Synthesis on Surfaces
+
Goals of texture placement
Take a 2D texture and wrap it onto a surface
Avoid noticeable seams between patchesAvoid noticeable seams between patches Minimize stretching and distortionMinimize stretching and distortion Produce a natural-looking resultProduce a natural-looking result
The next best thing
Lapped Textures – Praun Lapped Textures – Praun et al. – SIGGRAPH00et al. – SIGGRAPH00
Uses many overlapped Uses many overlapped texture patchestexture patches
Aligns patches with Aligns patches with underlying vector fieldunderlying vector field
Generally minimizes Generally minimizes distortiondistortion
The next best thing
Lapped texture’s Lapped texture’s shortcomingsshortcomings
Low-frequency Low-frequency componentscomponents
Boundary mismatchBoundary mismatch Direction field Direction field
singularitiessingularities
Texture synthesis to the rescue!
Process Create a mesh hierarchy over the modelCreate a mesh hierarchy over the model Set up a vector field over the meshSet up a vector field over the mesh Calculate sweep distance for each vertexCalculate sweep distance for each vertex Assign colors based on neighborsAssign colors based on neighbors
Process Create a mesh hierarchy over the modelCreate a mesh hierarchy over the model Set up a vector field over the meshSet up a vector field over the mesh Calculate sweep distance for each vertexCalculate sweep distance for each vertex Assign colors based on neighborsAssign colors based on neighbors
Mesh Hierarchy
Equivalent of a Gaussian pyramid to a Equivalent of a Gaussian pyramid to a surfacesurface
Multiple layers of different Multiple layers of different resolutionsresolutions
Each layer has 4 times the number of Each layer has 4 times the number of vertices of the layer above itvertices of the layer above it
Each layer contains every vertex of Each layer contains every vertex of the layer above itthe layer above it
Point placement
n points randomly placed on the surfacen points randomly placed on the surface Repulsion between the points spaces them Repulsion between the points spaces them
evenlyevenly These points are now fixed in place, These points are now fixed in place,
representing level m of an m-level meshrepresenting level m of an m-level mesh Repeated for each layer, adding 3 times Repeated for each layer, adding 3 times
more points each time (3n, 12n, etc)more points each time (3n, 12n, etc)
Connectivity
Connectivity between vertices of each layerConnectivity between vertices of each layer Delaunay triangulation appliedDelaunay triangulation applied Mesh is connected in a web of trianglesMesh is connected in a web of triangles
Mesh hierarchy operations
InterpolationInterpolation
Low-pass filteringLow-pass filtering
DownsamplingDownsampling UpsamplingUpsampling
Process Create a mesh hierarchy over the modelCreate a mesh hierarchy over the model Set up a vector field over the meshSet up a vector field over the mesh Calculate sweep distance for each vertexCalculate sweep distance for each vertex Assign colors based on neighborsAssign colors based on neighbors
Vector field
Provides order to the placement of the Provides order to the placement of the texture on the modeltexture on the model
Each mesh vertex is given a vectorEach mesh vertex is given a vector User initiates the process by defining a few User initiates the process by defining a few
key vectors (~12)key vectors (~12)
Vector field creation All vertices not user-defined set to 0All vertices not user-defined set to 0 User-defined vectors are downsampled to User-defined vectors are downsampled to
the coarsest meshthe coarsest mesh Low-pass filtering to fill out top meshLow-pass filtering to fill out top mesh Upsample for each layer to fill to bottomUpsample for each layer to fill to bottom
Process Create a mesh hierarchy over the modelCreate a mesh hierarchy over the model Set up a vector field over the meshSet up a vector field over the mesh Calculate sweep distance for each vertexCalculate sweep distance for each vertex Assign colors based on neighborsAssign colors based on neighbors
Surface sweeping
Uses the directional flow of the vector field Uses the directional flow of the vector field to assign ordering to the verticesto assign ordering to the vertices
Ordering will allow a sort of raster scan Ordering will allow a sort of raster scan over the 3D modelover the 3D model
The color in the imageThe color in the image
cycles as the sweepcycles as the sweep
distance increasesdistance increases
Sweep distance calculation
Select an anchor point to base the distanceSelect an anchor point to base the distance Each vertex takes the value that is the weighted sum Each vertex takes the value that is the weighted sum
of what its neighbors thinkof what its neighbors think Distance along the flow direction added to the Distance along the flow direction added to the
neighbor’s sweep distanceneighbor’s sweep distance
Sweep distances will propagate out from the anchor Sweep distances will propagate out from the anchor until every vertex has oneuntil every vertex has one
Process Create a mesh hierarchy over the modelCreate a mesh hierarchy over the model Set up a vector field over the meshSet up a vector field over the mesh Calculate sweep distance for each vertexCalculate sweep distance for each vertex Assign colors based on neighborsAssign colors based on neighbors
Pixel Neighborhoods
Similar technique to 2D texture synthesisSimilar technique to 2D texture synthesis Examine nearby colors and look for a Examine nearby colors and look for a
similar pattern in the texture imagesimilar pattern in the texture image Different kinds of pixel neighborhoodsDifferent kinds of pixel neighborhoods
Mesh coordinate space
Pixel neighborhoods don’t translate directly Pixel neighborhoods don’t translate directly to the unorganized vertices in a meshto the unorganized vertices in a mesh
Vertex vector is downVertex vector is down Rotate 90 degrees CCW for rightRotate 90 degrees CCW for right
Multi-level synthesis
Start at top, work downStart at top, work down Initialize the vertices of mesh layer k with Initialize the vertices of mesh layer k with
color values from Gaussian pyramid layer kcolor values from Gaussian pyramid layer k Make a pass with the half squareMake a pass with the half square Top layer should have a crude representation Top layer should have a crude representation
of the textureof the texture
Multi-level synthesis
Extrapolate and refine each lower levelExtrapolate and refine each lower level Extrapolate initializes the colors using Extrapolate initializes the colors using
a large full square neighborhood of the a large full square neighborhood of the level abovelevel above
Refine improves on that by combining Refine improves on that by combining a large full square on the current level a large full square on the current level with a small full square on the level with a small full square on the level aboveabove
Algorithm
Results
Results
Results
Results
Results
Results